Method for fabricating a bag with a flat bottom, and a bag thus obtained

ABSTRACT

A method for fabricating a bag with a flat bottom comprises: making a flattened tubular element with lateral bellows; obtaining a quadrilateral bottom of a single piece, the perimeter of which has a size equal to that given by the sum of the tubular element and the bellows; folding the bottom in a single piece along one of its first axes, keeping the outer sides parallel to the axis and of a size equal to the initial one; folding the other two sides to identify two opposite bellows, bringing a central folding line of the bellows thus identified into a position perpendicular to the first axis; inserting the bottom thus folded into the flattened tubular element, bringing the two opposite bellows of the bottom so that they are astride of the lateral bellows of the flattened tubular element; and welding the ends facing outwards of the flattened tubular element and of the corresponding lateral bellows respectively to the outer sides, which are parallel to the axis and are of a size equal to the initial size of the bellows and to the inner edges of the two opposite bellows obtained in the bottom. The bag has a quadrilateral bottom added to the tubular element and welded around the perimeter.

[0001] The present invention relates to a method for fabricating a bagwith a flat bottom and to a bag thus obtained.

[0002] In the field of automatic manufacture of bags, both bags withhandles (shopping bags or shoppers) and without handles (open-mouthedbags), it is normal to use as starting material a continuous tubularelement, which is, in general, made of thermoplastic material.

[0003] The aforesaid continuous tubular element is then provided, on itsopposite longitudinal sides, with appropriate areas turned inwards, inthe branch referred to herein as “bellows formation”, which enable it tobe amply developed in an open condition and enable a bottom having acertain width to be obtained, but one that is not flat.

[0004] In fact, once the continuous tubular element provided withlongitudinal side bellows formations is created, the next step in theprocess is to use an appropriately designed transverse welding rod,which functions intermittently, to form both the mouth (either opened orclosed) of the bag and the weld for closing so as to obtain the bottomof the bag, blocking both the opposite sides of the flattened tubularelement and the inner sides of the two bellows formations by means of asingle weld.

[0005] The use of the above bags is by now fairly widespread and isbound to continue increasing. The aforesaid bags are also used forcontaining objects having a certain weight, even though they present abottom of limited dimensions as compared to the transverse developmentthat the bag may have given by the sum of the sides of the flattenedtubular element and the size of the internal sides of the bellows allsplayed out together.

[0006] There is consequently felt the need to make bags with widerbottoms, for example, bags with flat bottoms, which will present acertain degree of sturdiness and a certain degree of strength.

[0007] So far, no solution has been found to the above rather importanttechnical problem.

[0008] The purpose of the present invention is therefore to identify asolution to the technical problem referred to above by making a bag witha wide flat bottom.

[0009] Another purpose of the invention is to provide a bag with a flatbottom that is particularly valid and that is able to perform thefunction outlined previously, which will be particularly simple toconstruct.

[0010] Yet a further purpose of the present invention is to provide abag with a flat bottom which will be able to be manufacturedautomatically, without any need for manual intervention for itscompletion.

[0011] The above purposes according to the present invention areachieved by providing a bag with a flat bottom and by a method forfabrication thereof, as set forth in the attached independent claims.

[0012] Further salient characteristics and details of the presentinvention form the subject of the dependent claims.

[0013] The characteristics and advantages of a bag with a flat bottomand of a method for fabrication thereof according to the presentinvention will emerge more clearly from the ensuing description, whichis provided purely by way of non-limiting example, of an embodimentthereof, with reference to the attached figures, in which:

[0014]FIG. 1 is a side view of a bag in a folded condition or positionmade according to the present invention;

[0015]FIG. 2 is a top plan view of a bottom element in a non-operativecondition, laid out flat, which must then be included in the bag of FIG.1 according to the present invention;

[0016]FIG. 3 is a perspective side view of the bottom element of FIG. 2in a folded condition ready for being inserted within the initialtubular element having an external shape that is the same as the oneillustrated in FIG. 1;

[0017]FIG. 4 is a perspective view, from beneath, of the bag of FIG. 1,when it is partially splayed out in an operative condition and isprovided with the flat-bottom element illustrated in FIGS. 2 and 3; and

[0018]FIG. 5 illustrates an enlarged view of a closed bottom end portionof the bag of FIG. 1.

[0019] With reference to the various figures taken as a whole, there isillustrated in an altogether schematic way a bag with a flat bottomaccording to the invention, designated, as a whole, by 11 and obtainedaccording to the method, which itself constitutes a novelty andinventive idea of the invention.

[0020] The bag with flat bottom 11 is obtained from a flattened tubularelement 12 provided with lateral bellows formations 13 folded towardsthe inside of the tubular element itself.

[0021] The bag 11, which is illustrated finished, envisages an openmouth 14 and a quadrilateral bottom 15, having in the case illustratedby way of example in FIG. 4 a rectangular shape, even though the saidquadrilateral bottom 15 may also be square.

[0022] In the folded condition, the bag 11 comprises a bottom element16, which is inserted inside an open end of the flattened tubularelement 12 with the free edges of both elements, towards the outside,set aligned and one on top of the other.

[0023] The bottom element 16 is made initially of a quadrilateral sheet(see FIG. 2), which is folded in a first direction into two halves alonga first folding axis 17, keeping two external sides or parallel edges 18parallel to said first folding axis 17 and so that they have a size thatis equal to the initial size.

[0024] Next, in a second operating step carried out on the aforesaidbottom element 16, the further two sides 19 are folded in order toidentify two opposite bellows 20 by bringing a central folding line 21of said bellows 20 thus identified into a position perpendicular to saidfirst axis 17.

[0025] Once the bottom element 16 has been folded as described above,said bottom element 16 is inserted into the aforesaid flattened tubularelement 12 by bringing the two opposite bellows 20 of said bottomelement 16 astride of the lateral bellows 13 of the flattened tubularelement 12.

[0026] In this way, the configuration and arrangement illustrated inFIG. 1 is achieved, except for the weld. In fact, it is at this pointthat the step of welding the ends facing the outside of the flattenedtubular element 12, opposite to the open mouth 14, with thecorresponding ends of the lateral bellows 20 of the bottom elements 16is carried out.

[0027] During the above operation, the outer sides 18 of the bottomelement 16 parallel to the first folding axis 17 are kept so that thesaid sides 18 are set aligned with the end of the flattened tubularelement 12. The weld is a perimetral weld, which constrains, in a firstportion 22, the sides that remain in view of the flattened tubularelement 12 with the sides 18 of the bottom element 16 and, in a secondportion 23, the sides of the internal bellows 13 of the flattenedtubular element 12 with the sides or internal edges of the two oppositeinternal bellows 20 of the bottom element 16; of course, this is donewhilst the latter are set in the folded condition on top of each other.

[0028] A perimetral weld is then made between the sides and the endbellows of the flattened tubular element 12 and the sides and thebellows of the bottom element 16, so obtaining a bag, which, in thesplayed-out and open condition has a quadrilateral flat bottom.

[0029] It is evident that a splayed-out and open bag provided with aquadrilateral flat bottom may be obtained also following steps otherthan the ones described previously, and hence the present invention alsoregards, in a much simpler manner, the said bag, irrespective of themethod with which it is obtained.

[0030] It has thus been seen how the said bag with flat bottom and themethod indicated according to the present invention achieve the purposesspecified previously.

[0031] The method of fabrication of a bag with flat bottom, as well asthe bag thus obtained according to the present invention, as conceivedherein, may undergo numerous modifications and variations all fallingwithin the scope of the same invention.

[0032] Furthermore, in practice, the materials used, as well as thedimensions and components, may be any whatsoever according to thetechnical requirements.

1. Bag with flat bottom obtained from a flattened tubular element (12)with side bellows (13), characterized in that said flat bottom isobtained from a bottom element (16), which is quadrilateral and has aperimetral weld, at the ends of the sides and of the bellows of saidtubular element.
 2. Bag with flat bottom according to claim 1,characterized in that said perimetral weld is made, in one of its firstportions (22), between the sides in view of the flattened tubularelement (12) with the first opposite sides (18) of said bottom element(16) and, in one of its second portions (23), between the sides of theinternal bellows (13) of said flattened tubular element (12) with theremaining two sides or internal edges of two opposite internal bellows(20) of said bottom element (16).
 3. Method for fabricating a bag withflat bottom, characterized in: making a flattened tubular element (12)with side bellows (13); obtaining a quadrilateral bottom of a singlepiece (15), the perimeter of which has a size equal to that given by thesum of said tubular element and said bellows; folding said bottom in asingle piece along one of its first axes (17), keeping the outer sides(18) parallel to said axis (17) and of a size equal to the initial one;folding the other two sides (19) to identify two opposite bellows (20),bringing a central folding line (21) of said bellows thus identifiedinto a position perpendicular to said first axis (17); inserting saidbottom element (16) thus folded into said flattened tubular element(12), bringing said two opposite bellows (20) of said bottom so thatthey are astride of said lateral bellows (13) of said flattened tubularelement (12); and welding the ends facing outwards of said flattenedtubular element and of the corresponding lateral bellows respectively tosaid outer sides (18) which are parallel to said axis (17) and are of asize equal to the initial size of said bellows and to the internal edgesof said two opposite bellows obtained in said bottom.
 4. Methodaccording to claim 3, characterized in that said bottom element (16) isobtained having a rectangular shape.